Tornado, auto reloading/parsing options when config file is modified.

demo.conf

greeting = 'Hello, World'

server.py

import functools
import logging
import os
import tornado.ioloop
import tornado.web

from tornado.options import define, options


class MainHandler(tornado.web.RequestHandler):
    def get(self):
        self.write(options.greeting)

application = tornado.web.Application([
    (r'/', MainHandler),
])


def load_options(config_file):
    define('greeting', default='Hello, world', type=str,
        help='Greeting string')
    tornado.options.parse_config_file(config_file)
    tornado.options.parse_command_line()

modify_time = None


def autoreload_config_file(config_file):

    def reload_options_on_update(config_file):
        modified = os.stat(config_file).st_mtime
        global modify_time
        if not modify_time:
            modify_time = modified
            return
        if modify_time != modified:
            logging.info('Modified config file, reloading options')
            modify_time = modified
            tornado.options.parse_config_file(config_file)
    callback = functools.partial(reload_options_on_update, config_file)
    tornado.ioloop.PeriodicCallback(callback, 500).start()


if __name__ == '__main__':
    config_file = 'demo.conf'
    load_options(config_file)
    autoreload_config_file(config_file)
    application.listen(8888)
    tornado.ioloop.IOLoop.instance().start()